The long term goal of this project is to refine and extend the process of gene transfer in cultured mammalian cells which can be presently achieved at low frequency with isolated metaphase chromosomes. The specific aims include: 1) detailed investigations of the process by which chromosomes are taken up and expressed by recipient cells, 2) determination of the fate of transferred materials both early in the process and after an established state has been achieved and 3) a detailed biochemical investigation of gene expression in "unstable" and "stable" gene transferents.